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What does past climate change tell us about global warming?

What the science says...

Select a level... Basic Intermediate

Greenhouse gasses, principally CO2, have controlled most ancient climate changes. This time around humans are the cause, mainly by our CO2 emissions.

Climate Myth...

Climate's changed before

Climate is always changing. We have had ice ages and warmer periods when alligators were found in Spitzbergen. Ice ages have occurred in a hundred thousand year cycle for the last 700 thousand years, and there have been previous periods that appear to have been warmer than the present despite CO2 levels being lower than they are now. More recently, we have had the medieval warm period and the little ice age. (Richard Lindzen)

At a glance

Just imagine for a moment. You fancy having a picnic tomorrow, or you're a farmer needing a dry day to harvest a ripe crop. So naturally, you tune in for a weather-forecast. But what you get is:

“Here is the weather forecast. There will be weather today and tomorrow. Good morning.”

That's a fat lot of use, isn't it? The same applies to, “the climate's changed before”. It's a useless statement. Why? Because it omits details. It doesn't tell you what happened.

Climate has indeed changed in the past with various impacts depending on the speed and type of that change. Such results have included everything from slow changes to ecosystems over millions of years - through to sudden mass-extinctions. Rapid climate change, of the type we're causing through our enormous carbon dioxide emissions, falls into the very dangerous camp. That's because the faster the change, the harder it is for nature to cope. We are part of nature so if it goes down, it takes us with it.

So anyone who dismissively tells you, “the climate has always changed”, either does not know what they are talking about or they are deliberately trying to mislead you.

Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!

Further Details

Past changes in climate, for which hard evidence is preserved throughout the geological record, have had a number of drivers usually acting in combination. Plate tectonics and volcanism, perturbations in Earth's slow carbon cycle and cyclic changes in Earth's orbit have all played their part. The orbital changes, described by the Milankovitch Cycles, are sufficient to initiate the flips from glacials (when ice-sheets spread over much of Northern Europe and the North American continent) to interglacials (conditions like the past few thousand years) and back  – but only with assistance from other climate feedbacks.

The key driver that forces the climate from Hothouse to Icehouse and back is instead the slow carbon cycle. The slow carbon cycle can be regarded as Earth's thermostat. It involves the movement of carbon between vast geological reservoirs and Earth's atmosphere. Reservoirs include the fossil fuels (coal/oil/gas) and limestone (made up of calcium carbonate). They can store the carbon safely over tens of millions of years or more. But such storage systems can be disturbed.

Carbon can be released from such geological reservoirs by a variety of processes. If rocks are uplifted to form mountain ranges, erosion occurs and the rocks are broken down. Metamorphism – changes inflicted on rocks due to high temperatures and pressures – causes some minerals to chemically break down. New minerals are formed but the carbon may be released. Plate tectonic movements are also associated with volcanism that releases carbon from deep inside Earth's mantle. Today it is estimated by the U.S. Geological Survey that the world's volcanoes release between 180 and 440 million tonnes of carbon dioxide per year - as opposed to the ~35 billion tonnes we release.

Epic carbon releases in the geological past

An extreme carbon-releasing mechanism can occur when magma invades a sedimentary basin containing extensive deposits of fossil fuels. Fortunately, this is an infrequent phenomenon. But it has nevertheless happened at times, including an episode 250 million years ago at the end of the Permian Period. In what is now known as Siberia, a vast volcanic plumbing-system became established, within a large sedimentary basin. Strata spanning hundreds of millions of years filled that basin, including many large coal, oil, gas and salt deposits. The copious rising magma encountered these deposits and quite literally cooked them (fig. 1).

Fig. 1: schematic cross section though just a part of the Siberian Traps Large Igneous Province, showing what science has determined was going on back then, at the end of the Permian Period.

Now laden with a heavy payload of gases, boiled out of the fossil fuel deposits, some of the magma carried on up to the surface to be erupted on a massive scale. The eruptions – volcanism on a scale Mankind has never witnessed - produced lavas that cover an area hundreds of kilometres across. Known as the Siberian Traps, because of the distinctive stepped landforms produced by the multiple flows, it has been calculated that the eruptions produced at least three million cubic kilometres of volcanic products. Just for a moment think of Mount St Helens and its cataclysmic May 1980 eruption, captured on film. How many cubic kilometres with that one? Less than ten.

Recently, geologists working in this part of Siberia have found and documented numerous masses of part-combusted coal entrapped in the lavas (Elkins-Tanton et al. 2020; fig. 2). In the same district are abundant mineral deposits formed in large pipes of shattered rock as the boiling waters and gases were driven upwards by the heat from the magma.

Fig. 2: an end-Permian smoking gun? One of countless masses of part-combusted coal enclosed by basalt of the Siberian Traps. Photo: Scott Simper, courtesy of Lindy Elkins-Tanton.

It has been calculated that as a consequence of the Siberian Traps eruptions, between ten trillion and one hundred trillion tons of carbon dioxide were released to the atmosphere over just a few tens of thousands of years. The estimated CO2 emission-rate ranges between 500 and 5000 billion tonnes per century. Pollution from the Siberian Traps eruptions caused rapid global warming and the greatest mass-extinction in the fossil record (Burgess et al, 2017). There are multiple lines of hard geological evidence to support that statement.

We simply break into those ancient carbon reservoirs via opencast or underground mines and oil/gas wells. Through such infrastructure, the ancient carbon is extracted and burned. At what rate? Our current carbon dioxide emissions are not dissimilar to the estimated range for the Siberian Traps eruptions, at more than 3,000 billion tons per century. The warning could not be more clear. Those telling you the climate's changed before are omitting the critical bit – the details. And when you look at the details, it's not always a pretty sight.

Last updated on 14 February 2023 by John Mason. View Archives

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Further reading

RealClimate article published by Prof. Stefan Rahmstorf on July 20, 2017:

The climate has always changed. What do you conclude?


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Comments 601 to 625 out of 901:

  1. Salute and thanks to Tom Curtis.

    To my knowledge, it has been just over 6 months since the last comment posted by Tom Curtis.   And I believe, about the same length of time since he posted at his blog "By Brisbane Waters"  [].

    Tom Curtis has been a frequent and energetic poster here at SkS, for 6 years or more.   He has researched / cited / quoted from a great deal of scientific literature, and he has analysed and discussed a great many issues.

    In short, he has been a powerhouse of objective scientific thinking.

    He has fought the good fight, against the lies lunacies & disinformation spread by anti-science propagandists & trolls.

    But over the years, Tom has occasionally referred to long-term unspecified health problems which hampered him.   His recent silence is unprecedented, and presumably indicates that he is too ill to post — or that Father Time has gathered him in.

    And I am sure that I speak for all science-oriented participants at SkS, when I express great thanks to Tom.


    (The moderators will, I hope, agree that this salute to Tom Curtis belongs here in the comments column of Climate Myth Number One , rather than in some difficult-to-find sub-listing.)

  2. Eclectic @601, thankyou for your kind words, and enquiry after my health.  I was advised of the enquiry after my health by Michael Sweet by Glenn Tamblyn in an email, and thought it appropriate to respond (with this being the best place).  As I have advised several of the SkS crew, my health problems have indeed worsened of late.  They are not life threatening, but have made the sustained pace of commentary I had shown in the past unsustainable for me.  As I find it difficult not to rebut silly arguments, or respond to requests for instruction, I doubt I could remain active on SkS in any capacity without being drawn into that high rate of activity, and so thought it best to absent myself completely.  On my last communication with an SkS team member, I mentioned that my health had improved and that I might be able to return to SkS in the medium turn.  Unfortunately it has now taken a turn for the worse, and that now looks less likely, although should my situation stabilize, I would certainly return.  In the meantime, I wish you all well, and succes to SkS and its mission.  

  3. Tom Curtis,

    It is very good to hear from you. I am sorry to hear about your health issues, my daughter has cronic health issues so I know they are a trial. I lived in Acacia Ridge for three years and I smile whenever I hear of Brisbane.

    Good luck with everything. I try to include a citation in all my posts but cannot detail things like you did. I wonder how you kept your patience with those who refuse to even read the data they are given.

    moderator: I accidently posted a duplicate of this on the wrong OP, sorry.

  4. I disagree with your statement that science has a good understanding of past climate changes and their causes. It does not. Also,Milankovitch was obviously brilliant to have figured out the spinning shifts of the earth. I believe he said that it might explain ice age cycles. Wikipedia gave a good explanation of the faults with that theory. I prefer my own theory listed as the Mike Krichew theory of what causes ice ages. So ask yourself the question: where does all the carbon dioxide come from in previous ice ages? I believe it came from warming oceans. This would explain why CO2 levels lag global warming in the data. So, what does the data say about warming oceans today. I have read that they are warming and thus giving off a lot more CO2 than our burning of fossil fuels now. Thus, I argue that even if we stop all fossil fuel burning today it will not stop global warming. 


    [JH] You are already skating on the thin ice of sloganeering by not providing science-based references for your own theories about what caused the ice ages and what is driving global warming.

    Sloganeering is prohibited by the SkS Comments Policy.

    Please note that posting comments here at SkS is a privilege, not a right.  This privilege can be rescinded if the posting individual treats adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Please take the time to review the policy and ensure future comments are in full compliance with it.  Thanks for your understanding and compliance in this matter.

  5. "where does all the carbon dioxide come from in previous ice ages? I believe it came from warming oceans"

    Conceded.  However, the rise in atmospheric concentration of CO2 driving the modern warming is NOT coming from the oceans, but from the human burning of fossil fuels.  This we know pretty thoroughly, due to the distinctive isotopic signature of the rise.  Also, we know that the rise in atmospheric CO2 is not from the oceans because the oceans are still acidifying.  This is well-understood by science and not contested in any meaningful way.

    Read this post for background.  If questions, place them there, not here.

    The Koch Industries-funded BEST team found that, WRT 'Is CO2 leading or lagging temperature rise':

    "we know that the CO2 is not coming from the oceans but from human burning of fossil fuels"


    "it is clear that it is the CO2 that comes first, not the warming"

    Due to the thermal lag of the oceans in response to the anthropogenically-forced warming imposed upon them, the world will continue to warm and its climate will continue to change, for decades after the cessation of the usage of fossil fuels.  Again, pretty well understood by science.

    This is a science- and evidence-based venue, with regulars well-versed in the science.

  6. Mkrichew @604 , your Mike Krichew theory was previously called the Murry Salby theory.   To see why Murry Salby was wrong, please read Climate Myth #142 (and elsewhere).

  7. mkrichew, your theory will have some serious hurdles to overcome in order to fit the present warming. The oceans are net carbon sinks at present, not sources; part of the gigantic amounts of carbon dioxide injected in the atmoshere go into solution in the oceans, and lead to acidification. There is an entire thread devoted to the subject on this site. Furthermore, what would be warming up the oceans in the first place? You'd have to find some seriously exotic source of heat to explain the kind of energy accumulation seen across the planet's oceans, another subject that is explored in SkS threads. Even if there was such a mysterious forcing, oceanic chemistry shows that they are not outgasing any CO2. I don;t feel obligated to link any references considering that all these considerations figure in already existing SkS threads. Use the search engine.

  8. " Also,Milankovitch was obviously brilliant to have figured out the spinning shifts of the earth." Not sure what you are trying to say here. He was brilliant, but for calculating the magnitude of the effects without a computer. The orbital cycles discovery is simply astronomical observation and discovery of some of them date back to ancient history (maybe Babylon).

    CO2 did come from oceans as they heated up at end of ice age cycles with significant contributions from eurasian swamps as well. If you want a new theory, make sure it matches the observations of methane as well and also accounts for the isotope composition of both in ice cores.

    However, ocean outgassing from current warming is not happening yet - not even close. You cannot seriously posit a new theory that violates basic physical and chemical laws and observations.

    " I have read that they are warming and thus giving off a lot more CO2 than our burning of fossil fuels now."

    You dont say your source but it is clearly untrustworthy. The actual fluxes are well established as the mass of papers associated with that diagram in the IPCC report show.

  9. Unless there is confusion between an outward flux and the net flux. It is "voodoo economics" to have amount of CO2 dissolved in oceans increasing (the reducing pH) while claiming net outflow from ocean to atmosphere.

  10. What I found so astounding about the claim that because climate change happened before and that therefore CO2 is not the cause is a non sequitur. Because on does not follow the other. First of all the far past was significantly different in rate of change and second the distribution and amount of sequistiring green biomass was a whole lot more than it is now. There were intact ecosystems that could balance the change. And ecosystems had ample time to adapt to the change. This is not happening now. Humans are decreasing green biomass a lot. There are even less ecosystems now compared to then. I think this alone debunks a lot of this natural change myths happening now. If I am incorrect please indulge me and explain it to me. 

  11. aemilius89 @610,

    I would correct one thing you say. Yes, humans are reducing the area of the globe which support 'ecosystems'. But, dispite their best efforts, humans are not decreasing green biomass. A significant proportion of our CO2 emissions do result from cutting into the 'green biomass' (this the source of an average of 13% of our total CO2 emissions since AD2000 according to Global Carbon Project global budget). That proportion is a lot smaller than it used to be. It was 62% a century ago and 89% fifty years before that, these large numbers because back then  fossil-fuel-use was in its infancy. Yet these emissions which represent 'decreasing green biomass' have to be balanced against the extra CO2 'land sink' which with the falling proportion of land use emissions now exceeds those land use emissions (GCP figures put the 'land sink'  at 30% of emissions total emissions throughout) and the sink has exceeded source since about 1965.

    Mind, I could go all pedantic and add that had you said 'us humans had decreased the green biomass' this statement would be supported by the GCP data (which goes back to 1860) as the cumulative net loss of biomass in the century prior to 1965 still just exceeds the cumulative net gain in the half century since. We'll need another half decade to achieve parity between cumulative loss and gain. (This timing dependent on a 1860 start date which we could at a pinch get away with as providing a pre-industrial value.)

  12. In my comment 594, I suggested that 'the climate's changed before' or 'climate always changes' is really only half an argument, with two possible misleading inferences, and only one of these is really covered in depth here (although they are both enumerated in the blob points of the intermediate article). I'm hoping this comment might be useful if revising, clarifying or expanding these pages.

    Dr Richard Milne, University of Edinburgh biologist, makes exactly this point and puts these fallacies more clearly and entertainingly than I can in his lecture 'Critical Thinking on Climate Change: Separating Skepticism from Denial', covering both in two minutes, before employing the Scotese graph of temperature over geological time(!), and moving on to his next myth,

    The first implication is 'the climate's changed before... therefore it must be natural', is covered a bit in the intermediate article, and the logical fallacy is deconstructed in very similar terms by John Cook, Peter Ellerton and David Kinkead in their fun video. (By the way, does the assertion that there's no lag actually run counter to the usual explanation of lag but feedback? Probably mentioned elsewhere in these comments.)

    Their paper on critical thinking could equally be applied to the second  implication: 'the climate's changed before ... so it's nothing to worry about'. Milne characterises this as 'A didn't harm B, when B was not present, therefore A cannot harm B'. I'm suggesting that as some people move from 'phase 1' dismissal (it's not happening), through 'phase 2' (it's not us), most dismissives are moving to 'phase 3' (it's not bad), so this second implication is worth clarifying.

    So I think having articles from knowledgeable people on the following would be great, and then they could be hold the findings and be linked from a general page about the fallacies:

    • Previous warming during the Holocene hasn't adversely affected civilisation (in some cases it did, warming was smaller and slower and local, the Optimum was before settlements, we caused some of it through deforestation, the pattern of warming was different, larger future warming is projected to adversely affect ecosystems, food supplies etc.)
    • Previous hyperthermal events like the PETM (or P-T boundary) didn't necessarly lead to mass extinctions or runaway climate change and the Earth was 'resilient'. (Sometimes it does lead to mass extinction, depending on rate of change as well as absolute temperature, weathering will reduce CO₂ only over millennia, most extinctions involved climate change, solar radiation has increased, and our perturbations are on the scale of these extinctions, tended to wipe out megafauna, we have some idea of the extinction and range shift rates, this is a long-term change; much as in the basic article here)

    Tangentially related because I can't think where else to suggest it, probably under 'it's not bad' or 'it's too hard':

    • The projections are imprecise and there are lots of uncertainties about impacts, therefore we shouldn't act until these are resolved, or it might turn out OK (risk management principles; uncertainty means range, not doubt; some range is inevitable; we know more than might be thought; climate change is non-linear and affects some regions more severely than others)

    Finally, I note there's nothing under the 'it's too late' heading in the taxonomy, which is related to the opposite idea, that size of warming is completely unprecedented in the Cenozoic. I occasionally meet overstatements of the kind 'boreal forest will collapse; there will be a permanent El Niño', although these seem individual and not as repetitive as the climate dismissives. Climate Feedback deals with these when they happen, and if there's time, it may be worth seeing how a sceptical analysis looks at those.

  13. Responding to jesscars from here:

    Sigh, "OK, so you are saying that the effect of CO2 on the temperature is only minor. "

    No, he was saying the CO2 direct contribution to ice ages is 0.5C. Mostly it is an amplifier (feedback) converting a change in northern NH albedo into global event.

    Historically CO2 can change for many reasons, depending on which events you are talking about. Volcanoes, change to sea temperature (CO2 solubility), changes to vegatation cover, long term carbon sequestration in rock, freeze/thaw of tundra swamps, operating on time periods of seasons to eons. The pliestocene ice-age cycle is driven by milankovich.

    Climate is always a response to sum of all forcings. (solar input, albedo, aerosols, GHGs). Past climates are considered by looking at what changes to all of them. Complicating matters is that temperature change triggers feedbacks - you cant change temperature without also changing CO2, CH4, water vapour and albedo.

  14. We are told at the end of the video that climate is understood.  If that is the case, then why are climate models not capable of reproducing climate history over the past 35 years?

  15. Waterguy13 @ #614 ,

    What source do you base your comment on?   The earlier mainstream climate models have done a fairly good job with their projections during the past 30 years or so.   They can be criticized for minor inaccuracy, in that they A) somewhat overestimated the tropical mid-trospheric "hot spot" , and B) underestimated arctic warming,  and C) underestimated sealevel rise.

    But on the whole, they have done quite well.   In comparison, Dr Lindzen's model has done appallingly badly [he predicted cooling!] . . . and Lindzen still has difficulty acknowledging the reality of the actual ongoing global warming.

    Waterguy13 , you very much need to explain your strange comment.

  16. The "science" statement here seems incredibly overly bold and lacking in sufficient supporting scientific corroberation.

    "GHGs, principally CO2 have controlled most major climate changes"?

    That seems like quite a leap of faith. It seems like changes in solar behavior, volcanism, impacting comets and meteors, seismic activity, and who knows what else would be tough to rule out.

    The accompanying video appears to address a strawman argument in that skeptical references to prior climate change, specifically warming are not to argue that "therefore current warming must also be natural" but rather that it may be natural, or at least mostly natural.

    On the skeptics' side an opposing science versus myth scenario plays out, where an AGW argument is offered that "it must be anthropogenic since the current/recent warming is unprecedented in magnitude and/or rate." Well, that just isn't true, is it?

    The claim appears to assume high confidence in our understanding of all the various ocean systems' natural heat cycles with periods ranging in scale from decadal, to multidecadal, to century scale, and millennia scale. But aren't we now just beginning to learn about the various systems and cycles of ocean heat transport?

    The science claim appears to also assume high confidence in our understanding of various natural albedo cycles and feedbacks, and also of multiple cyclic and random solar behavior, and also geomagnetic influences.

    If Earth's natural climate response includes a combination of various natural cycles of various periods, then shouldn't we be having a very careful comprehensive look to identify ALL of such cycles, and then very thoroughly analyze ALL of them jointly rather than just dismiss each in turn for failing to fully cause recent observed behavior?

    How do we know that what we've recently witnessed in the observed temperature record isn't mostly just the result of a so-called perfect storm scenario, a coincidence of multiple cyclic peaks? If we cannot know that, then how can we know that equilibrium climate sensitivity to a doubling of atmospheric CO2 isn't a benign or even beneficial 1.5°C, not the claimed 3°C?

    That is the point of referring to proxy temperature records that indicate greater magnitudes of temperature and greater rates of temperature change. It is to say, hold on amigo, maybe we best not jump to such a bold conclusion prematurely; cause there's likely a lot we still don't know concerning climate, and so shouldn't we take some more time to be sure we comprehensively understand nature before calling the international 911 climate change SWAT team?

    It appears to me that this particular myth-busting is premature.

    The next 20-30 years of observations may prove highly informative, one way or the other.  If needed, we can pretty easily pump aerosols into the atmosphere while we ramp up nuclear power plants and renewables.  No?  

    Party on and be excellent to each other my brothers! And sisters, if there be any of the finer gender here. :)


    [PS] Please look at articles under the "arguments" to understand why the statement is soundly based in scientific observation and not a leap of faith. Better still, try reading the IPCC WG1 report to understand what the science actually says. Uninformed statements about what you presume science assumes do not helpful to any discourse. You would see that the science has actually carefully examined all known influences on climate and quantified these with error bars.

  17. Ed,

    You say "It seems like changes in solar behavior, volcanism, impacting comets and meteors, seismic activity, and who knows what else would be tough to rule out."  Fortunately, scientists have been working hard on these questions for the past 100 years.  They have been able to make the difficult observations you have apparently missed.  Looking at all the data we see that, in fact, scientists have shown that CO2 was responsible for almost all of past catastrophic climate change.

    Read the references that the moderator linked to find out how all this is known.

    I note that you have cited zero scientific reports in your post.

  18. Dear PS:

    That was a quick response!  Thank you for that.

    "...try reading the IPCC WG1 report to understand what the science actually says. Uninformed statements about what you presume science assumes do not helpful to any discourse. You would see that the science has actually carefully examined all known influences on climate and quantified these with error bars."

    I'm not uninformed.  I'm a well-published (dozens of peer-reviewed papers) science professional who's become interested in this subject.  I've read the recent WG1 report, noted the error bars and confidence levels, and that's a big part of the reason for my posting here.

    After some forty years of additional observations, intense scrutiny, supercomputer modelling, satellite technology, and massive capital investment, the stated range of estimated equilibrium climate sensitivity (ECS) to a doubling of CO2 remains unchanged at 1.5°C to 4.5°C.  

    Climate omniscience seems still a very long way off.  Don't you agree?

    If I get a chance, I'll post links to some of the recent literature dealing with as yet unquantified natural forcings and feedbacks.


    [PS] Range for ECS (which is problematic because of feedbacks) has nothing to do with attribution of cause which you were querying. Scientific critique of the attribution chapter in the WG1 is welcome. Be sure to comment on the appropriate topic - use the search function to help find one. If you had read WG1, then why all the false presumptions?

  19. Ed the Skeptic @616 : you say you are not uninformed ~ yet you seem unaware of the absurdity of suggesting that the modern-day rapid global warming could be caused by "multiple cyclic peaks" of warming.   (e.g. Dr Curry's frequent "hints" that oceanic cycles are the majority cause of recent rapid warming, are similarly absurd.)

    The "multiple peaks" hypothesis is unphysical [=absurd] because:

    A.  Oceanic currents merely redistribute heat energy, giving negligible overall change through a full cycle.  (Unusual events, such as the Younger Dryas, produce a forcing feedback via albedo change ~ but that is not-at-all the case in the present circumstances.)

    B.  There is no evidence of significant positive [=planetary heating] effect from other cycles or Natural Variations that you mentioned, during the recent 50 years of rapid surface temperature rise.  And the real temperature rise is still going up steeply.

    C.  If the oceans were producing the observed surface heating, then there would be some consequent cooling of the upper ocean.  But actually the opposite is occurring ~ the oceanic water is warming [Oceanic Heat Content is increasing over many decades].

    D.  Even assuming that a "perfect storm" is presently existing ~ leads to the necessity of having a simultaneous Unknown Mysterious Cooling Factor which counteracts the known planetary warming effect of our recent atmospheric CO2 rise (and other GHG's).   Some Mysterious Cooling Factor that nicely follows/matches the rising arc of CO2.   Clearly absurd !

    Ed, our past climate change tells us global warming occurs when there is a reason causing the change.   The evidence is strong enough to indicate that we should abate the present [Greenhouse] cause.

  20. Ed says earlier in the thread "changes in solar behavior, volcanism, impacting comets and meteors, seismic activity, and who knows what else would be tough to rule out."

    Certainly not for recent times. None of these is a factor in the changes we are currently experiencing. Solar activity is actually lower now than it was in the late 20th century (see related threads where PMOD data can be found). Comets and asteroid strikes have a way of getting noticed. Even tiny nuclear weapon tests in North Korea can be detected by our seismological equipment. "Who knows what else" seems to be falling in the category of cosmic rays and Leprechauns (see applicable thread, except for Leprechauns), rather surprising from one who claims an extensive scientific background.

    Perhaps, like a lot of other people, Ed has difficulty accepting that we humans are responsible for a truly geological scale event. Going up in total atmospheric CO2 content by a 100 ppm within the 2ish decades since I started teaching weather for pilots is simply astounding, and a lightining fast geological freak event. Anyone who doesn't see that has a problem with quantitative thinking. Human activity releases about 100 times more CO2 per year than all volcanoes together (see applicable thread). If all of a suddent we started witnessing that kind of volcanic activity, year after year, there would be absolutely no doubt about its scope, consequences, and the urgency of the situation.

  21. I've read the other myth-busting pages.  Lots of good information on many of them.  I hope to engage on some that appear deficient from my semi-informed perspective.  I have no dog in this hunt other than truth and scientific integrity.  I'm disappointed by the personal commentary that some se fit to include. 


    Defendping consensus scientific orthodoxy ought be done with humility, lest you join the ranks of the scoffers and naysayers who pilloried the likes of Copernicus, Galileo, Einstein, and LeMaitre.

    I'm not seeing lots of hard scientific evidence here on this myth-buster topic,  just mostly declarations.  Thus my posting.

    This myth-busting deals with natural climate variability, yes? Isn't the uncertainty about ECS exactly directly related to that?  It's wide range informed by some decadeal to millennial scale proxy temperature records—GISP2 stands out—would seem to indicate a significant uncertainty related to this topic, no?  That's the only intended point.

    Can anyone engaged hereing please explain the apparent certainty on the issue offered here on SKS relative to figure 8.14 and 8.15 of AR4 WG1?  

    Has anyone seen the NASA data showing significant decadal reduction in global cloudiness from around the 1980-2000 time frame, dropping from roughly 70% to 65% in two decades?  That drop in cloudiness corresponds with an apparent increase in global surface solar radiation of roughly 4 W/m^2.  

    Where is that addressed in the AR4 WG1 tally of radiative forcing information included in the aforementioned figures 8.14 amd 8.15?


    [DB] Baiting snipped.

  22. The above-mentioned cloudiness data for your convenience:

    LINK 1

    Correlation with temperature change:

    LINK 2

    This is data is not being shared to divert topic, just to ask where it is included in the above-mentioned IPCC AR4 WG1 figures.


    [DB] Shortened links breaking page formatting

  23. Ed @ 621/622 ,

    you don't really advance your case (whatever it is) by waving a rhetorical hand in the direction of Copernicus, Galileo, Einstein, and LeMaitre.

    Copernicus and Galileo were (strictly speaking!) representing the scientific consensus of their age (an age of very few scientists, indeed).   Their opponents (shall we label them denialists?) were a group of rich & powerful men (in the upper echelons of the Papal state) who supported an evidence-deficient position. Easy to see a parallel with the rich & powerful magnates of the upper echelons of the fossil fuel industry . . . plus c'est la meme chose.   Even more irony, in that the modern-day Pope denounces those same science-deniers.

    Einstein and LeMaitre advanced the physics/astrophysics science ~ but they did not trash the pre-existing body of science.

    # Attacking the consensus scientific orthodoxy [especially in climate matters] ought to be done with humility [and genuine skepticism], lest you join the ranks of the Dunning-Krugerites.


    "Uncertainty" about ECS (currently the most probable ECS figure being around 3 or 3.5 degrees) is an interesting scientific question ~ but in no way justifies delaying on decently fast transition to a nett-zero-emission economy.   After all, we citizens/voters/politicians/parents ought to be intensely practical in prudent risk-managing. 

    My apologies, but my little laptop is struggling to access "figure 8.14 and 8.15 of AR4 WG1".   Perhaps, Ed, you would be kind enough to upload those charts and explain how you think they undermine the mainstream position.

    Strangely, the same goes for Dr Humlum's "climate4you" illustrations.  (I have no difficulty accessing the WUWT and Climateetc websites.)   On the little I know of Dr Humlum: he has (scientifically speaking) a poor track record indeed.   * That is not to say he must therefore be wrong, on the cloudiness issue.  But it seems the somewhat-related "Iris Hypothesis" of Prof Lindzen has fallen flat on its face.  And on a second point: a "cloudiness drop" providing a warming forcing of "roughly 4 W/m^2" has much the same problem I mentioned above in post #619.D  . . . that if true, then there must also be some Unknown Mysterious Cooling Factor that nicely follows/matches the rising arc of CO2's warming forcing effect.   Which seems absurdly unlikely, if not quite impossible.

    (And which would leave only another 5 impossible things to believe before breakfast.)

  24. The IPCC figures mentioned @621 are:-

    IPCC AR4 Figure 8.14.

    IPCC AR4 Figure 8.15.

    The graphics linked @622 are reporduced by the denialist website climate4you from the now defunct International Satellite Cloud Climatology Project but discussion of these data would be best transferred to a more appropriate thread - SkS Could global brightening be causing global warming?

  25. Ed,

    You claim that you are "semi-informed".  You are citing resources that are  at least 10 years out of date.  The current IPCC report is AR5 or the 2018 supplimental report.  Perhaps the discrepancy you notice is caused by SkS being up to date while your reference is out of date.

    You are clearly echoing some other web site you have read.  Can you cite and link that web site directly so that we can see the entire argument?  SkS probably addressed this myth in an OP 10 years  ago when it was first raised.  It will be easier for us to directly address the source instead of rehashing the argument again.

    When you claim to be semi-informed attacking consensus scientific orthodoxy ought be done with humility,  If the best you can find is a 10 year old web site that is no longer active you might want to reconsider how strong your argument is.

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